Florida Department of Transportation’s Enhanced Hydroplaning Prediction Tool

Florida Department of Transportation (FDOT) recently developed and implemented a new hydroplaning prediction (HP) program for predicting the traveling speed at which a vehicle would start hydroplaning. The tool was developed as part of the effort to reduce hydroplaning accidents and is being used during the roadway design phase to evaluate the hydroplaning potential of Florida’s roadways. This paper presents an overview of FDOT’s HP program and demonstrates how it may be used. The tool incorporates a total of four water film thickness models and three hydroplaning speed models developed in the past, allowing for a total of 12 model combinations for the hydroplaning analysis. The tool also offers different analysis options that may be used to meet a variety of FDOT’s needs. As demonstrated in this paper, the primary use of the new HP tool is for checking the final geometric roadway design parameters for hydroplaning potential. In addition, the HP program can also be used as a forensic investigation tool for identifying specific locations that exhibit higher potential for hydroplaning.

Evaluating Relationships between Perception-Reaction Times, Emergency Deceleration Rates, and Crash Outcomes using Naturalistic Driving Data

Perception-reaction time (PRT) and deceleration rate are two key components in geometric design of highways and streets. Combined with a design speed, they determine the minimum required stopping sight distance (SSD). Current American Association of Highway Transportation Officials (AASHTO) SSD guidance is based on 90th percentile PRT and 10th percentile deceleration rate values from experiments completed in the mid-1990s. These experiments lacked real-world distractions, and so forth. Thus, the values from these experiments may not be applicable in real-world scenarios. This research evaluated (1) differences in PRTs and deceleration rates between crash and near-crash events and (2) developed predictive models for PRT and deceleration rate that could be used for roadway design. This was accomplished using (1) genetic matching (with Rosenbaum’s sensitivity analysis) and (2) quantile regression. These methods were applied to the Strategic Highway Research Program 2 (SHRP2) Naturalistic Driving Study (NDS) data. The analysis results indicated that there were differences in PRT and deceleration rates for crash and near-crash events. The specific estimates were that, on average, drivers involved in crash events took 0.487 s longer to react and decelerated at 0.018 g’s (0.58 ft/s2) slower than drivers in equivalent near-crashes. Prediction models were developed for use in roadway design. These models were used to develop tables comparing existing SSD design criteria with SSD criteria based on the results of the predictive models. These predicted values indicated that minimum design SSD values would increase by 10.5–129.2 ft, dependent on the design speed and SSD model used.

Accuracy Comparison of Aerial Lidar, Mobile-Terrestrial Lidar, and UAV Photogrammetric Capture Data Elevations over Different Terrain Types

Lidar and other remotely sensed data such as UAV photogrammetric data capture are being collected and utilized for roadway design on an increasing basis. These methods are desirable over conventional survey due to their efficiency and cost-effectiveness over large areas. A high degree of relative accuracy is achievable through the establishment of survey control. In this case study, elevations (z-values) derived from mobile-terrestrial lidar, aerial lidar, and UAV photogrammetric capture collected with survey control were statistically compared to conventionally surveyed elevations. A cost comparison of the methods is also included. Each set of z-values corresponds to a discrete horizontal point originally part of the conventional survey, collected as cross-sections. These cross-sections were surveyed at three approximate tenth-mile sample locations along US-30 near Georgetown, Idaho. The cross-sections were collected as elevational accuracy verification, and each sample location was selected as an area where the mobile-terrestrial lidar in particular was expected to have more difficulty achieving accuracy off the road surface. Processing and analysis were performed in Esri ArcMap 10.6, and all data were obtained from the Idaho Transportation Department, District 5. Overall, the aerial lidar elevations were found to be closest to conventionally surveyed elevations; on road surface and level terrain, mobile-terrestrial and UAV photogrammetric capture elevations were closer to the conventionally measured elevations.

Validation of Bicycle Level of Traffic Stress and Perceived Safety for Children

The level of traffic stress (LTS) methodology was developed to measure, track, and improve the suitability of bicycle networks. Thanks to the simplicity of its data needs and interpretation, LTS has been implemented by several states, regions, cities, non-profits, and researchers. However, relatively few validations of the methodology exist. There is a specific gap in relation to safety perceptions for children, an important group since it serves as the critical population for LTS 1. This study validates LTS using a survey of parents in Denver, Colorado, in which they are asked about perceived safety and biking allowance relative to roadway design characteristics. After the LTS score and biking allowance rates for 612 roadway scenarios are determined, a one-way analysis of variance (ANOVA) is used to determine the suitability of LTS for children. Findings suggest that while LTS 1 and LTS 4 align well with stated preferences, parents told that their children would be able to tolerate some roadway conditions—when allowing for adult supervision—that are currently considered LTS 2 or even LTS 3. These scenarios are primarily on low-volume roadways that have bike lanes. By further refining LTS, it is hoped to ensure that all populations have access to safe and comfortable bicycle facilities.

Roadway Backfill Mining with Super-High-Water Material to Protect Surface Buildings: A Case Study

As coal resources trapped under surface buildings in the Wangtaipu coal mine area impede the efficient mining of coal seams and constrain the sustainable development of coal mines, a super-high-water roadway backfill mining technique for preventing building damage was adopted. According to the control principle and theoretical calculations, an engineering design was established including the reasonable width of segment coal pillars in the working face and technical parameter design. The monitoring results after the implementation of the scheme showed that building deformation was controlled within grade I, protecting the surface buildings. A reasonable roadway design parameter was achieved, with a surface subsidence of 27 mm and horizontal deformation of 0.3 mm/m, indicating that it can ensure the safety of surface buildings from the State Bureau of Coal Industry. The practical trial can provide a reference for the extraction of coal resources under similar conditions and is vital for the sustainable development of the mining industry and economic growth.

Familiar versus Unfamiliar Drivers on Curves: Naturalistic Data Study

Human factors studies have shown that route familiarity affects driver behavior in various ways. Specifically, when drivers become more familiar with a roadway, they pay less attention to signs, adopt higher speeds, cut curves more noticeably, and exhibit slower reaction times to stimuli in their peripheral vision. Numerous curve speed models have been developed for purposes such as predicting driver behavior, evaluating roadway design consistency, and setting curve advisory speeds. These models are typically calibrated using field data, which gives information about driver behavior in relation to speed and sometimes lane placement, but does not provide insights into the drivers themselves. The objective of this paper is to examine the differences between the speeds of familiar and unfamiliar drivers as they traverse curves. The authors identified four two-lane rural highway sections in the State of Indiana which include multiple horizontal curves, and queried the Second Strategic Highway Research Program (SHRP2) database to obtain roadway inventory and naturalistic driving data for traversals through these curves. The authors applied a curve speed prediction model from the literature to predict the speed at the curve midpoints and compared the predicted speeds with observed speeds. The results of the analysis confirm earlier findings that familiar drivers choose higher speeds through curves. The successful use of the SHRP2 database for this analysis of route familiarity shows that the database can facilitate similar efforts for a wider range of driver behavior and human factors issues.

Analyzing Pedestrian and Bicyclist Crashes at the Corridor Level: Structural Equation Modeling Approach

Pedestrian and bicycle crashes have been increasing at an alarming pace in recent years. Between 2009 and 2016, annual U.S. pedestrian fatalities increased 46%, and bicyclist fatalities increased 34%. Crashes involving pedestrians and bicyclists, or vulnerable road users (VRUs), are negatively correlated with roadway factors, and positively correlated with environmental and socioeconomic factors. However, specific variables representing these factors are often correlated, making it difficult to accurately characterize relationships between individual variables and pedestrian and bicyclist safety. This study used the structural equation model technique to overcome this problem. Pedestrian and bicyclist crash frequency and more than 60 explanatory variables for 200 highway corridors in Wisconsin were collected. The interrelationships between observed “manifest” variables and unobserved “latent” variables were tested. The results suggest that the most important latent variables influencing the crash frequency of VRUs are bicycle/pedestrian-oriented roadway design (e.g., paved shoulders, sidewalks, and bike lanes), exposure (e.g., walking and biking activity, and employment density), and low social status (e.g., educational level, and wage percentage). The benefits of this study may help community planners, transportation researchers, and policymakers with a better understanding of the intricate interrelationship of the influential factors contributing to VRUs road crashes.

A Study on Use of Plastic Coated Aggregates (PCA) in Bituminous Concrete Mixes of Flexible Pavement

The continuous increase in road traffic and heavy loading in combination with insufficient maintenance due to paucity of funds has resulted in deterioration of road network in India. To improve this proper maintenance, effective and improved roadway design, use of better quality materials and use of effective and modern construction techniques should be put into practice. During last three decades in many countries around the world it has been tested that modification of the bituminous binder with plastic/polymer additives enhances the properties and life of bituminous concrete pavements. The present investigation was carried out to propose the use of plastic coated aggregate (PCA) in bituminous mix of flexible pavements in order to improve their performance and also to give a way for safe disposal of plastic wastes in order to counter environmental pollution as well. There are mainly two processes available for incorporation of waste plastic in bituminous concrete mixes namely wet and dry process. In this study the dry process was used for bituminous concrete mixes as it being simple and economical. Physical properties of conventional and plastic coated aggregates were compared. The Marshall method of mix design was adopted using VG-10 grade bitumen for conventional aggregates and plastic coated aggregates (PCA). Marshall Specimens were prepared at bitumen content ranging from 4% to 6% with a increment of 0.5% by weight of aggregates and with waste plastic content of 5%, 7%, 9%, 11%, 13% and 15% by weight of optimum bitumen content. Marshal stability, Flow value, Air voids (Vv), Voids in mineral aggregates (VMA), and Voids filled with bitumen(VFB) were determined and compared with conventional aggregates (without plastic) bituminous concrete mixes. It was found that there was a reduction in consumption of bitumen in bituminous concrete mix by use of plastic coated aggregates also a considerable improvement in the properties of aggregates and bituminous concrete mix leading to provide longer life and improved pavement performance.